1. Field
The present application relates to voice telephony, and more particularly to transport setting up and authorizing of voice calls involving mobile devices.
2. Related Art
Voice telephony remains a major application of interest for business and personal use. In an example corporate setting, a telephony installation at a site can have a large number of users connected to a Private Branch Exchange (PBX) server, which can interface those users to a smaller number of outside lines (e.g., an E1 or T1 line) (a PBX can be implemented using a server with telephony cards for example). A PBX can interface with other servers and systems, such as one or more application servers that can provide enhanced services to devices connected to the PBX, such as mobile devices. For example, a PBX can interface with an application server over an IP connection, using SIP signaling. Services provided by an application server can include third party call control, enterprise voice mail, single number reachability, call forwarding, park, and conferencing, for example. PBX systems also can communicate with each other over trunk lines, and packet networks, depending on implementation.
A PBX can perform services for a voice call, based on direction from an application server. For example, a PBX can initiate an outgoing call to a number specified by an application server using SIP signaling to the PBX. A PBX also can provide information about incoming calls to an application server. For example, a PBX can provide ANI information, to an application server, for a call incoming to the PBX, which may be provided a service by the application server. Where data communication is unavailable with a mobile device, the mobile device would not have an IP address (or more generally, where mobile device cannot acquire an IP address), authentication mechanisms available in SIP cannot be used.
It is desirable to provide an experience to devices being serviced from such systems that is responsive, while also maintaining a measure of authentication to be able to use the systems, to reduce undesirable situations such as abuse or unauthorized access.